Even beginners can learn to respond to classroom commands in the target language.
The conversation session is designed to be the time when the student is completely immersed in the language, so keeping the session in the target language is essential. This is the one opportunity all week that the student has to practice the language with peers, so no time should be lost in English. Tell students that during the last 5 minutes of the session they may ask questions in English if they still need to and then stick to the target language.